The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.
FIGS. 1A and 1B are diagrams of a protocol structure for supporting a dual connectivity technology employed by a conventional network.
A Packet Data Convergence Protocol (PDCP) layer supports efficient data transfer by using network protocols such as IPv4 or IPv6. In particular, for efficient transmission of IP packets, the PDCP layer uses a header compression method for compressing header information of packets.
A Radio Link Control (RLC) layer, which is subordinate to the PDCP layer, constitutes an RLC Packet Data Unit (PDU) of a size suitable for radio transmission, and it performs an Automatic Repeat Request (ARQ) function that is responsible for retransmission of a lost RLC PDU during transmission. The transmit-side RLC layer constructs an RLC PDU suitable for transmission by using a segmentation and concatenation function of an RLC Service Data Unit (SDU) passed from the higher level. The receive-side RLC layer performs a data reassembly function to reconstruct the original RLC SDU. The RLC layer has an RLC buffer for storing RLC SDUs or RLC PDUs.
A MAC layer transfers data received from the RLC layer to a terminal or a gateway.
FIG. 1A is a protocol structure for supporting a dual connectivity technology by using a core network (CN) split method.
The structure of the protocol using the CN split method has relatively low complexity. Therefore, in the conventional network, such protocol structure can be introduced without major change compared to the earlier protocol structure prior to supporting the dual connectivity technology. The structure of the protocol using the CN splitting method is equivalent to a conventional protocol structure with only a specific bearer passed to another base station (Secondary eNodeB, SeNB).
The master base station (Master eNodeB or MeNB) receives only an MCG bearer. The MCG bearer corresponds to a bearer which transfers data by using only the radio resources of the master base station. As with the master base station, the secondary base station (Secondary eNodeB or SeNB) receives only an SCG bearer. The SCG bearer, which has the same structure as the MCG bearer, is adapted to transfer data by using only the radio resources of the secondary base station.
FIG. 1B is a protocol structure for supporting a dual connectivity technology using the PDCP splitting method.
The dual connectivity technology using PDCP splitting method is a technology for separating bearers from the PDCP layer of one base station. Unlike the existing protocol structure, the structure of the protocol using the PDCP splitting method has two RLCs connected to one PDCP. This protocol structure allows one bearer to transfer data by using both the master base station and the secondary base station.
The master base station receives split bearers along with MCG bearers. A split bearer is a bearer that transfers data by using radio resources of the master base station as well as the secondary base station.
The existing network (LTE) has greatly improved the data transfer rate by using such dual connectivity technology. However, in the next-generation network, the maximum possible data transfer rate compared with the existing network is several tens of times higher, and this fact makes it difficult to provide the next-generation network simply with the system architectures that have served the existing networks.
Therefore, there is a growing need for a new network structure in which an existing network and a next-generation network cooperate to provide an appropriate network according to the state of the terminal or the network.